Traditional basement walls are made from masonry materials, which typically include concrete or stone. The masonry materials may be cement blocks or poured concrete. A 2″ foam insulation barrier is commonly placed on the outside of the foundation wall. A vapor and/or water barrier is thereafter placed over the insulation. Then the exterior space may be back filled with crushed stone, gravel or sand. The above ground back fill is then grade downwardly away from the building.
Masonry foundation walls are typically cold in the winter. Often the basement and crawl spaces have a musty odor as moisture can wick-up through the cement walls from below. Mildew, leakage and dampness are common and problematic for masonry foundation walls in buildings. Finishing the basement of a building with masonry walls is difficult and expensive. Egress doors, windows and escape exits require cutting and extraction of the masonry walls. Inside framed wood walls with insulation and a moisture barrier are also common, but expensive.
Pressure-treated wood was developed in the 1960s. Permanent foundation wood used in foundations is treated by steam-impregnating it with a chemical called CCA (chromated copper arsenate) at a concentration of at least 0.6 pounds of chemical per cubic foot of wood so that the chemical penetrates deep into the core of the wood. The copper part of the compound is toxic to fungus, mold and bacteria, while the arsenate is toxic to pests like carpenter ants and termites. Other pressure and non-pressure treatment options include: borates, amommiacal copper quantenary (ACQ) and pentachlorophenols. Other wood treatments are in development and expected to enter the marketplace in time. With these advances, it has become possible for wood to be used in foundation walls without being prohibitively vulnerable to damage from insects and moisture. By the 1070s, permanent wood foundations (PWF) gained acceptance.
Long-term durability is attainable with a sound wood foundation that is properly constructed. When wood foundations fail, the case is almost always due to poor construction techniques. Strength is achieved by following guidelines laid out in wood foundation manuals. The deeper into the ground, the stronger the wall needs to be. Choice of 2×6″, 2×8″ or 2×10″ wall studs must be made correctly along with stud spacing and sheathing thickness. Ground pressure at the bottom of the foundation wall is resisted by the floor slab. Ground pressure at the top portion of the foundation wall is resisted because the foundation wall is anchored to the building floor system with hangers and clips. The intermediate ground pressure is resisted by proper selection of dimensioned wall studs, center-to-center stud proper spacing and outer sheathing thickness. Usually the sheathing is sealed with caulk and wrapped to cover the sheathing and header with an overlapping 6 mil polyethylene film and adhesively sealed to the sheathing and header. All water is typically filtered through the backfill, footings, and fill underneath the slab where the water is collected and pumped away by a sump pump or drained to the above ground if the building is built on a hill. Wood foundation costs are cheaper than concrete block or poured walls. Inside finishing is much easier and cheaper because you are finishing a stud wall.
Referring to prior art FIG. 1, the general construction of a permanent wood foundation wall 10 may be seen and understood. The permanent wood foundation 10 consists of treated wall studs 12 properly spaced and secured to treated footing plates 14 and a header plates 16. On the outside of the wall studs 12, exterior wall sheathing 18 is secured and sealed at its joints by moisture-proof caulking sealer. Lastly, a polyethylene 6-mil moisture barrier sheet or film 20 is placed over the foundation wall 10 to above ground covering the exposed foundation in an overlapping manor and adhesively sealed thereto. A plywood plank 30 protects the exposed poly film 20 above ground.
Below the footing plates 14 is a gravel base and footings 22 on top of which is placed a bottom polyurethane moisture barrier 24 that extends throughout the interior space of the foundation. Thereafter a floor slab 26 is poured and allowed to cure. Insulation 28 is placed or sprayed between the wood foundation wall studs 12 that consist of insulative materials which might be glass fiber, mineral wool, cellulose or sprayed polyurethane foam. A polyethylene moisture barrier film (not shown) is secured over the interior of the foundation wall studs 12. Drywall (not shown) is then secured to the inside of the wood foundation wall studs 12. Graded back fill 34 then fills in the exterior space on the outside of the foundation wall 10. Above ground floor joists 31 are supported by the foundation walls 10 upon which is secured floor panels 30 to complete floors 32. For purposes here, the first above ground floor 32 is supported by floor joists 31 which may be 2″×6″, 2″×8″, 2″×10″ or 2″×12″ depending upon the floor support requirements.
Concerning above the ground walls, Applicant's prior U.S. Pat. Nos. 9,677,264 and 9,783,985 thoroughly discuss and show prior building walls and their shortcomings. In these patents Applicant discloses and claims composite thermal break wood studs with rigid insulation, mechanical fasteners and wall framing systems.